A mystery illness is killing East Anglia’s hares – sparking a call for the public to report sick animal sightings and help researchers diagnose the disease.

During the past month, landowners, farmers, dog-walkers and householders have reported seeing sick and dead hares in areas around Bungay, Diss and Thetford.

Despite laboratory analysis of the carcasses, animal health experts have so far been unable to establish what is causing the deaths.

So the Norfolk and Suffolk Wildlife Trusts are joining with the University of East Anglia to ask anyone seeing a freshly dead hare to record its location, photograph the entire animal, and send the information to Dr Diana Bell at the University of East Anglia.

Dr Bell has recently been studying the impacts of diseases on rabbit populations, including myxomatosis and strains of rabbit hemorrhagic disease (RHD).

She said: “The death of any animal is obviously distressing but we’re asking people to try and photograph these hares to help us understand what is happening.

“Getting good images of the bodies of these hares, along with their exact location, is crucial for us to rule out or identify possible diseases.”

Dr Bell said the first report was received on September 13 from a dog-walker in Bungay, who had seen a sick hare which was later found dead in the same spot. The carcass was sent to an Animal and Plant Health Agency laboratory, which was unable to diagnosis the illness.

“In the autumn we tend to get mortalities from coccidiosis, which is a parasitic disease with diarrhoea symptoms, but this hare didn’t have those symptoms,” said Dr Bell.

“We know we have got widespread RHD in rabbits and we are waiting to see if it will jump to hares. When we did the post-mortem it had hemorrhagic lungs, but it was not found in the liver.

“There was another report from a couple near Diss who had a hare dying in their garden. It ended up having quite dramatic convulsions, and it was very distressing.

“I started to ask other people and the Suffolk Wildlife Trust were getting reports of what Defra defines as mass mortalities – which is three or more dead animals in a small area. They had reports of three and six hares dead in the same field.

“We need information from the public and we need to do post-mortems to find out what is killing these animals.”

East Anglia is an important stronghold for brown hares, which have experienced a national decline of more than 80pc in the past 100 years, attributed to factors including the intensification of farming, which has limited their supply of food and habitat.

There is also no closed season for hares, which means that they can be shot legally at any time of the year, and illegal hare coursing is a rising rural concern.

John Milton, head of nature reserves at Norfolk Wildlife Trust, said: “The brown hare is such an iconic species and they are not only important as wildlife, but they also contribute to the habitat of areas like the Brecks with the wild grazing they do alongside rabbits.

“So this is potentially another concern for us along with the hemorrhagic disease which has been affecting our rabbits.”

Ben McFarland, head of conservation at Suffolk Wildlife Trust, said: “The reports of hare deaths are obviously of great concern, especially considering the importance of the populations in this region.

“We are monitoring all sites closely and asking anyone who sees an animal that is dead or unwell to get in touch.”

Hares can be distinguished from rabbits in a number of ways: Hares are larger than rabbits, with longer hind legs and black-tipped ears that are as least as long as their heads.

• Have you seen a sick or dead hare? Send a photograph of the hare including its head and bottom to Dr Diana Bell at the UEA by emailing d.bell@uea.ac.uk or calling 01603 592177.